An LIE system of which the specifications are formulated in 3GPP (3rd Generation Partnership Project), which is a project aiming to standardize a mobile communication system, supports downlink multi-antenna transmission (for example, see Non Patent Document 1).
In order to realize the downlink multi-antenna transmission in the FDD scheme, a user terminal feeds back a combination of precoder matrix information indicating a precoder matrix and rank information indicating a rank, to a base station. The precoder matrix determines the transmission directionality, and the rank determines the number of signal sequences (number of layers).
The base station performs the downlink multi-antenna transmission by applying the precoder matrix and the rank based on the feedback information (a combination of the precoder matrix information and the rank information) fed back by each user terminal.